I'm not sure if the '69s are different but my "old school" mechanic changed my rear main last fall without taking the engine out or removing the flywheel. went smoothly and no leaks.

What seal was put back in ?A rope seal really needs to be packed in the groove in the block and cap to be seated correctly.A lip type seal needs to have a sealant used or it will eventually spin.Also both type seals need to be trimmed perfectly.

It was the rear mail seal that was replaced. The old rope type seal was forced out and the new two piece lip type seal rotated in with sealant. I was skeptical too but the mechanic, a good friend of mine, said he has done it before. We will see if it makes it through the summer. It has been run a few times since the install and no signs of any leaks yet. I'll keep you posted.

Hank,That’s great. I reconditioned my engine but I stayed away from the rear seal because I thought that I would need to remove crank etc. I think I will try toremove mine. Any tips you can give me would be great. I have the engineout

I used the Viton crank seal too, but still had oil leaks. There was thread here I think some years ago, about how the Pontiac rear seal cut-out wasn't machined well enough (not round) to use a Viton seal.There is an old/antique tool, kinda looks like Chinese finger trap that's made for replacing the rear main seal with the crank in place. Never used it, but it may work if you want to use the rope seal. I have replaced a formed rubber seal in the car with crank in place (different kind of car & engine) before. It's a bit of a PITA but it can be done.

-=>Lee<=-Due to budget constraints the "light at the end of the tunnel" has been turned off!

One has to be able to drop the pan enough to get the rear cap off. The BOP rear seal is pushed through the groove with sealant on the end a few times to fill the rope seal anti-rotation holes. once filled the seal is then wiped clean an rotated through a few more times to clean the groove.the seal is then slid in and the cap is placed on with the other half of the seal and torqued down. The BOP rear seals are very good.

trouble is some of the seal grooves are not concentric or the mains have been machined so many times the groove has tightened up on the top and bottom. That happened to me and I had to make a tool to remachine the groove.

One has to be able to drop the pan enough to get the rear cap off. The BOP rear seal is pushed through the groove with sealant on the end a few times to fill the rope seal anti-rotation holes. once filled the seal is then wiped clean an rotated through a few more times to clean the groove.the seal is then slid in and the cap is placed on with the other half of the seal and torqued down. The BOP rear seals are very good.

trouble is some of the seal grooves are not concentric or the mains have been machined so many times the groove has tightened up on the top and bottom. That happened to me and I had to make a tool to remachine the groove.

My 400 HO is sitting on my test stand. Maybe I will give it a try... replace the rear seal with crank & pistons still on.

That's gotta be brutal to do under the car. But I guess if you have a hoist maybe it's not that bad.

With my motor on a stand, I disassembled the main caps and rod caps and removed the crank without removing the pistons or the heads. I got the crank ground and got new bearings and new 1 piece rear seal and reassembled.

When I first bought the Firebird, I replaced the seal with the engine in the car by lifting it slightly off the mounts and dropping the pan. I managed to remove all the caps and lower the crank just a bit to use the rope seal tool to pull out the old seal and install the 'TIN INDIAN" seal. Didn't last long so I pulled the engine out. That resulted in a rebuild. The mains were bored at least three times. I put in the 'graphtite' seal. That lasted about 1000 miles. I pulled it again and found the crank was brown around the seal area from heat. I measured the rear seal grove, it was WAY out of round. About 16-20 thou out at the cap and the block.

I tried a dozen machine shops trying to get someone to re-machine the groove. No luck! A one piece chebby? yes, a Pontiac no. I thought a machine shop would want to do something besides bore out SBCs all day long. I contacted a shop in Tenn that would do it but it was $800 for shipping.

I bought some 1-1/4" round ground steel and some !" plate aluminium. I made two doughnuts to fit into the bearing bores and some clamps to hold the shaft in the correct position. A hole drilled through the end of the shaft to hold a cutting tool such as those in a lathe. I got the cutting bit from KMS tools. I shaped the cutting edge the same profile as the seal groove. A threaded hole drilled 90 degrees to the first one was used to hold the cutting edge in place with a lock bolt.

After positioning the tool in the block I moved the cutting edge out so it just touched the groove and gave it a few turns, then loosened the lock bolt and moved it out a couple thou. I measured the groove after every adjustment and eventually took 18 thou off the cap and 12 off the block.

I assembled the engine with the BOP two piece chevron seal, after around 6-7000 miles it still didn't leak.

A lot of machine shops have hundreds of thousands of $$$ in machinery, I've got a drill press a bench vise and a press.Machinist used to love a challenge and a change in routine. I guess they are a dying breed. Too bad.

When I first bought the Firebird, I replaced the seal with the engine in the car by lifting it slightly off the mounts and dropping the pan. I managed to remove all the caps and lower the crank just a bit to use the rope seal tool to pull out the old seal and install the 'TIN INDIAN" seal. Didn't last long so I pulled the engine out. That resulted in a rebuild. The mains were bored at least three times. I put in the 'graphtite' seal. That lasted about 1000 miles. I pulled it again and found the crank was brown around the seal area from heat. I measured the rear seal grove, it was WAY out of round. About 16-20 thou out at the cap and the block.

I tried a dozen machine shops trying to get someone to re-machine the groove. No luck! A one piece chebby? yes, a Pontiac no. I thought a machine shop would want to do something besides bore out SBCs all day long. I contacted a shop in Tenn that would do it but it was $800 for shipping.

I bought some 1-1/4" round ground steel and some !" plate aluminium. I made two doughnuts to fit into the bearing bores and some clamps to hold the shaft in the correct position. A hole drilled through the end of the shaft to hold a cutting tool such as those in a lathe. I got the cutting bit from KMS tools. I shaped the cutting edge the same profile as the seal groove. A threaded hole drilled 90 degrees to the first one was used to hold the cutting edge in place with a lock bolt.

After positioning the tool in the block I moved the cutting edge out so it just touched the groove and gave it a few turns, then loosened the lock bolt and moved it out a couple thou. I measured the groove after every adjustment and eventually took 18 thou off the cap and 12 off the block.

I assembled the engine with the BOP two piece chevron seal, after around 6-7000 miles it still didn't leak.

A lot of machine shops have hundreds of thousands of $$$ in machinery, I've got a drill press a bench vise and a press.Machinist used to love a challenge and a change in routine. I guess they are a dying breed. Too bad.

That's awsome!! You must be a machineist or were one to come up with that idea. My 67 bird has a 75 400. I will attempt a rear seal job asap for iit's leaking like a siv. Probably go with a two piece seal, I believe that's what those engines had. I'd like to do the job with the eng in the car. I hope there aren't any issues like you had.

No not a machinist, I was Chief Engineer at an Aircraft repair and maintenance facility. I started out in the bush working on Beavers, Otters, 185s, Norseman. Beach 18s, DC3s. Then worked for two schedule and charter airlines, more turbine powered aircraft and helicopters, then a few jet propelled aircraft. While visiting my Folks on Pender Island, I was offered the Chief Engineer position. I phoned my girlfriend in La Ronge, who told me it was 49 below zero there, it was 49 above here, easy decision. Not a profitable career change, but I wasn't freezing my [censored] every winter. Now I have a sawmill business.

The small journal engines didn't have the same problems with the eccentric rear seal groove as the large journal engines did. Yes, yours had a two piece robe seal but I would use the BOP two piece chevron seal. There is a rope seal remover and installation tool to pull the rope seals and reinstall with the crank still in the block, but I have more faith in the BOP seal.

Do yourself a favor and just pull the engine to replace that seal. You'll save yourself some time and a lot of aggravation. Plus you'll get a good look at everything and will be able to take care of any other issues that you may find. If there aren't any other problem areas you have peace of mind knowing you did everything you could.

Just checking back in. Going on most of two summers and probably 4K miles and still holding on. My friend, the shop owner said at the time, let's try this, if it doesn't hold then we'll get serious and pull the motor.

Mine is leaking as well. I generally do not use stop leak products but wonder if any of the new ones actually work. Read some good feedback/reviews on these two: ATP-205 or Lucas engine stop leak. Anyone try them?

So lets think about this for second...the holes that feed oil to your crank and cam bearings are, for the most part, pressurized oil leaks. You really do not want to goo them closed. How does a stop leak oil additive differentiate between a good leak and a bad one? Just sounds like a bad idea to me. But then I'm no expert that's for sure.

So lets think about this for second...the holes that feed oil to your crank and cam bearings are, for the most part, pressurized oil leaks. You really do not want to goo them closed. How does a stop leak oil additive differentiate between a good leak and a bad one? Just sounds like a bad idea to me. But then I'm no expert that's for sure.

I good stop leak is polite and asks the part if it’s ok to “filler up” before it does it. Lol